1. Field of the Invention
The present invention relates to a device to close an opening in an airfoil, and more particularly a device to close an opening in an airfoil leading edge which results from deploying a leading edge flap or slat.
2. Background Art
Aircraft wings are commonly designed with leading edge flaps or slats which have a retracted position for cruise, and a downwardly and forwardly extended position for high lift operation, such as in takeoff and landing. In the cruise configuration, the flaps or slats generally conceal the main or fixed leading edge structure of the airfoil, but in the deployed position, the surface of this leading edge structure of the airfoil is exposed to airflow, in circumstances where, for example, the flap or slat forms with the main leading edge structure a slot for flow of air therethrough. Generally, there is some type of connecting member extending between the flap and the wing structure, such as a track which supports the flap, or a servicing member such as a telescopic thermal anti-icing duct. In some circumstances, it is necessary for these interconnecting members to penetrate (i.e. extend) through the skin forming the leading edge surface of the main airfoil structure. It sometimes happens that in the movement of the flap or slat from the retracted to the deployed position, these interconnecting members move relative to the leading edge opening in the main wing structure so that the opening in the skin of the leading edge structure must be made larger than the connecting members themselves. Such open areas at and above the leading edge must be closed off to prevent the unfavorable effects that such openings so located have on an airfoil, particularly the effect of increasing the stall speed caused by the flow disturbance resulting from the openings.
The conventional apparatus for closing off the undesired opened areas have been in the form of various types of sliding and curtain seals. These have not been totally satisfactory with regard to such things as, for example, durability. Another problem in providing such a closure device for these leading edge openings is that sometimes the open space available inside the main leading edge structure is rather limited, because of the presence of structural components or other apparatus.
A search of the patent literature has revealed a number of patents relating to closing various openings or gaps in aerodynamic structure. These are noted below.
U.S. Pat. No. 2,381,680, Maxwell, shows a leading edge device for an airfoil where the leading edge device can be moved to a deployed position to form a slot. The leading edge device itself is provided with a slot cover which closes the slot when the leading edge device is retracted for cruise configuration. U.S. Pat. No. 2,381,679, also issued to Maxwell, shows a similar arrangement.
U.S. Pat. No. 3,968,946, Cole, shows an extendable aerodynamic fairing. In this arrangement, there is a leading edge flap which is rotated outwardly to a deployed position. A gap is formed between the inboard end of the leading edge flap and the adjacent structure. Accordingly, there is an extendable fairing which rotates outwardly from the adjacent structure to close this gap.
U.S. Pat. No. 4,042,191, Johnson, illustrates a flexible seal that closes a gap which exists between a Krueger-type flap and the leading edge surface of the main wing structure. The pressure differential caused by the air flowing over the upper wing surface moves the seal into its closed position.
French Pat. No. 1,011,175 illustrates what appears to be a member which rotates about an axis generally parallel to a spanwise axis of an airfoil to close a gap in a surface forming a leading edge slot.